When to use a Web framework ?

Hi.
I'm wondering, When to use a web framework (like Struts, JSF, Tapestry, Spring MVC) ?
What are the kinds of applications that are best implemented using a framework ?
(Forums, Weblogs, online store, banking system ....)
What do you think ?

Some people will say always use a web framework. Others will say never use one. There really isn't a good answer to this kind of question. A (good)framework can make applications easier to develop. This has been talked about quite a bit so just search for other similar questions. You might search the Struts forum as well since it used to be a general Framework discussion point.